1. Field of the Invention
The present invention relates to a keyboard-type tone plate percussion instrument that generates a musical tone when a corresponding tone plate is struck by a corresponding percussion unit in response to a key depression operation, and relates to a resonance tube and a resonance box for a tone plate percussion instrument that cause a musical tone generated by a tone plate to resonate therein.
2. Description of the Related Art
As disclosed in Japanese Utility Model Laid-open Publication (Kokai) No. H05-081895, there has been known a keyboard-type tone plate percussion instrument including tone plates and percussion units such as hammer action units and adapted to generate a musical tone of a specific tone pitch when a corresponding tone plate is struck by a corresponding percussion unit in response to a key depression operation.
In this keyboard-type tone plate percussion instrument, the tone plates are fixed for vibration to a supporting part of the instrument by means of a pin or the like, resonance boxes are provided each having an opening side thereof arranged close to the tone plates, and each percussion unit is disposed below a corresponding tone plate. The just-mentioned mechanism is constructed in an upper and lower two-stage fashion. Specifically, the tone plate group, percussion unit group and resonance box which correspond to white keys are arranged in an upper part of the percussion instrument, whereas the tone plate group, percussion unit group and resonance box corresponding to black keys are arranged in a lower part of the instrument.
The aforementioned two-stage structure is needed mainly to meet a demand that each resonance chamber of the resonance boxes must have the required width large enough to achieve a satisfactory resonance function, which cannot be achieved if the resonance chamber is too small in width in the direction in which the tone plates are arranged. For this reason, as in the case of the aforementioned prior art, the tone plate percussion instrument is ordinarily provided with resonance boxes constructed into an upper and lower two-stage fashion, thereby making it easy to ensure the required width of each resonance chamber of the resonance boxes.
In the conventional tone plate percussion instrument, there are used different types of resonance boxes for different ranges. Specifically, Helmholtz-type, closed-tube type, and single-type resonance boxes are used in an increasing order of tone pitch as seen from the side of the lowest tone range of the instrument. Each resonance chamber of the resonance boxes has an opening thereof that opens toward the tone plates and is fully closed on the side thereof opposite from the tone plates.
Among these resonance boxes, the single-type resonance box has a single resonance chamber common to a plurality of tone plates associated therewith, whereas the Helmholtz-type and closed-tube type resonance boxes each have resonance chambers corresponding to respective ones of a plurality of tone pitches concerned, wherein each resonance chamber is constructed to have a natural resonance frequency, so as to cause a musical tone of a tone pitch (frequency) generated by a corresponding tone plate to efficiently resonate therein.
To this end, the closed-tube type resonance box is mostly constructed such that the resonance chambers thereof are different in length and hence different in volume to have different natural resonance frequencies from one another. As for the Helmholtz type resonance box, the resonance frequency of each resonance chamber can be adjusted by varying the opening area of its opening (port) that opens toward tone plates. In the above-described conventional tone plate percussion instrument, therefore, the tube length and port opening area are variously combined to differentiate the natural resonance frequency between the resonance chambers.
However, in the conventional tone plate percussion instrument having the resonance box of an upper and lower two-stage structure, the tone plates and the percussion units must also be constructed into an upper and lower two-stage structure, resulting in the following disadvantages.
First, the percussion instrument requiring the two-staged resonance box becomes large in size as a whole. Furthermore, long coupling rods are required for transmission of key depressing operations to the lower percussion unit group, resulting in a further increase in the entire size of the instrument. In addition, the provision of the coupling rods results in not only complicated construction and increased weight of the instrument but also heavier feelings in operating the lower percussion units than in operating the upper percussion units. To unify key-depression feelings between when the upper percussion unit is operated and when the lower percussion unit is operated, the feeling in operating the upper percussion unit must be adjusted to be close to the feeling in operating the lower percussion unit, which disadvantageously results in heavy key-depression feeling as a whole.
Furthermore, since the tone plate group corresponding to the white keys is vertically separated in position from the tone plate group corresponding to the black keys, the sounding position differs between these two groups, and therefore, the volume of sound and how the sound is heard by the listener vary between the two tone plate groups depending on the listener position, making it difficult to balance sounds therebetween. In addition, musical tones sounded by the upper tone plates are interrupted by the lower tone plate group, lower percussion unit group and lower resonance box, making it difficult to efficiently output sounds. This poses a problem that it is difficult to attain well-balanced appropriate sounds.
As explained above, it is essentially required to construct the resonance box and the like into a two-stage structure in order to ensure that each resonance chamber of the resonance box has the required width, which poses problems such as the increased entire size of the musical instrument. Similar problems are also encountered in tone plate percussion instruments provided with no percussion units.
Moreover, especially in the closed-tube type resonance box, the resonance frequency of each resonance chamber can only be adjusted by adjusting the volume of the resonance chamber. In addition, the resonance chambers must be so arranged as to correspond to the array of the tone plates, and hence the resonance chamber is limited in width size in the direction in which the tone plates are arranged. As a result, the resonance frequency of each resonance chamber is adjusted solely by varying the tube length. As a consequence, the size especially the height size of each resonance chamber is fixed, which disadvantageously lowering the degree of freedom in design.